: Natural History

Into June and we have selected silicon as our element of the month. This element might not be instantly recognisable as of significance to Wales, but it does have an interesting history.

Silicon (chemical symbol – Si), atomic number 14, is a hard but brittle crystalline solid, with a blue-grey metallic lustre. Silicon is the second most abundant element (about 28% by mass) in the Earth’s crust after oxygen with which it has a strong affinity. Consequently, it took until 1823 for a scientist - Jöns Jakob Berzelius – to prepare it in pure form.

In Wales, silicon is present virtually everywhere in one form or another: from quartz (silicon dioxide, SiO₂) in sedimentary siltstones, sandstones and conglomerates; complex silicates in igneous and metamorphic rocks; to sediments in soils.

Silica (silicon dioxide, or quartz) was mined extensively in the Pontneddfechan area, in South Wales, from the late 18^th century until 1964 for the manufacturing of firebricks for kilns and furnaces. It occurs as a very pure material highly concentrated in quartzite within a geological unit known as the Basal Grit. Weathering and erosion of the quartzite has produced deposits of silica sand and this was extensively quarried for the production of refractory fire bricks for the smelting industries.

In North Wales, a little-known trade in rock crystal – a colourless, glassy variety of quartz crystal – took place in Snowdonia during the 18^th and 19^th centuries centred upon the village of Beddgelert. T. H. Parry-Williams refers to this in one of his writings. Miners and mountain guides searched for veins of quartz in the mountains and collected crystals to sell to tourists as curios and some were possibly used to make crystal chandeliers. Later, crystals were occasionally discovered in the vast slate quarries, or during the large-scale construction of forestry tracks during the 1960s.

Silicon, as silica (another name for silicon dioxide) is also important to certain organisms. In particular diatoms and sponges.

Diatoms are single-celled microscopic algae with a complex cell wall made of silica. They are abundant in all waters, produce oxygen and are food for other aquatic organisms. Diatoms are also frequently used to monitor water quality.

Sponges build their skeletons from a framework of tiny elements called spicules, which are made of silica in most sponge groups.  One of the most beautiful examples is the Venus’ Flower Basket glass sponge, which lives anchored to the deep ocean floor near the Philippines.  A pair of shrimps lives inside this sponge, breeding inside it and spending their whole lives protected within its delicate glass walls.  Thanks to this unusual symbiotic relationship, the dead skeletons of Venus’ Flower Baskets are a popular wedding gift in Japan.

Sponges are the most primitive kind of animal on Earth, and their resistant spicules are found as fossils from as far back as 580 million years ago. Silica is also important in the preservation of other types of fossil.  When dead animals or plants are buried, silica from groundwater can fill in the pores and other empty spaces in wood, bone or shells, and/or it can replace the original remains as they decay or dissolve.  This is most common in areas where the groundwater has high silica levels, due to volcanic activity or erosion of silica-rich rocks.  The organic remains act as a focal point for silica formation, and often the rock surrounding the fossils is made of different minerals.  For example, shells that were originally made of calcium carbonate can dissolve and be replaced by silica, whilst being fossilised within limestone (calcium carbonate).  Extracting the fossils is a simple process of putting the rock in some acid and waiting for it to dissolve, leaving behind the silicified fossils.  The Museum’s fossil collections include many silicified shells of brachiopods, ammonites, bryozoans and other sea creatures.

One of the most spectacular types of fossil preserved in silica is ‘petrified wood’.  Silica replaced the original cells of the wood as it decayed and also filled in any gaps, literally ‘turning it to stone’.  In some places, including Patagonia and the USA, whole tree trunks replaced by silica are found in so called ‘petrified forests’.  Other plant fossils, such as cones, can also be fossilised in this way.

Chert is a rock made of very small crystals of silica.  Many major chert deposits formed at the bottom of ancient oceans from ‘siliceous ooze’, which is made of the skeletal remains of millions of tiny organisms including diatoms and radiolarians (single-celled plankton).  Chert nodules can also form within other rocks through chemical processes. 

Chert found within chalk is known as flint, and was a very important material for making tools throughout Prehistory. Tools are made by knapping, that is striking a prepared flint edge, or striking platform, with a harder stone to detach pieces called flakes or blades. These flakes, blades, and indeed the core from which they are struck can then be modified with secondary working into fine tool forms. Amongst the most skilful are fine arrowheads, including these from a Bronze Age grave at Breach Farm, Vale of Glamorgan, Wales. Flint was generally the material of choice for making sharp cutting tools as it is so fine-grained and fractures conchoidally and cleanly it gives a really sharp cutting edge. Indeed, so much so, that anecdotally eye-surgeons are reported to occasionally use a freshly struck flint blade in the operating theatre!

Because it is very fine-grained and hard, chert can preserve fossils of very small things from far back in our planet’s history.  The oldest potential fossils on Earth are found in cherts, and include the possible remains of bacteria from over 3 billion years ago.  Younger fossils, from the Rhynie Chert of northern Scotland, provide a glimpse of one of the earliest land communities, 400 million years ago.  Simple plants, and animals including primitive spider-like creatures and scorpions, were preserved in fine detail thanks to silica-rich water from volcanic hot springs.

Opal is a hydrated form of silica, meaning that it contains between 3 and 21% water.  Unlike standard silica, it does not have a set crystal form, but some of its forms diffract light, creating a beautiful iridescent effect in a variety of different colours.  For this reason, opal has been prized for centuries as a gemstone for making pendants, rings and other jewellery.  Australia produces a lot of the world’s opal, and is also a source of rare and spectacular opalised fossils.  The shells of invertebrates such as belemnites (prehistoric squid-like creatures), and even dinosaur bones, have been replaced by opal, creating very colourful specimens in a world where fossils are usually grey or brown.

Within Amgueddfa Cymru’s botany collections are books of dried plant specimens created by scientists and enthusiasts. Each specimen has been carefully dried and pressed, before being added to the books, sometimes with handwritten or printed notes alongside. The books are of enormous importance both in terms of modern scientific research into climate change and biodiversity, and as a way to see first hand the history of botanical exploration.

You can now look through a catalogue of the 36 books that contain non-flowering plants, fungi, lichens and seaweeds. You can read about a few of the stories surrounding these books below. For more detailed information about each book, please visit the website.

These books show the changes in how we collect, classify and name plants over two centuries from 1800 to present day. An old volume which probably dates from the 19^th century entitled “New Zealand Mosses”, contains more than just mosses. Lichens, algae and even some pressed hydrozoans (tiny marine animals) have been included by the unknown collector who chose to group these superficially similar ‘moss-like’ specimens together. This donation entered the Museum’s collections after its Royal Charter was received and before work had begun on the present Cathays Park building.

While the earliest currently known non-flowering plant specimen in the Museum is a moss collected in 1794 from Gwynedd, the earliest specimen book dates from 1803. This book is Lewis Weston Dillwyn’s personal collection of seaweed and freshwater algae collected between 1803 and 1809. Dillwyn’s specimen book was donated to the Museum in 1938 by the National Library of Wales, and has great importance both scientifically and historically.

Lewis Weston was part of the influential Dillwyn family, and his son John Dillwyn Llewelyn became an early pioneer photographer. He was interested in the natural history that he saw in south Wales where he lived. This is reflected in his scientific research as well as in the pottery designs created while he was owner of Cambrian Pottery. Dillwyn described new species of algae and his specimen book contains type specimens (irreplaceable specimens used in the original description of a species). The book is a personal record of his scientific life, recording places he visited and scientists who sent him specimens. He became a Fellow of the Royal Society in 1804 and later had a plant genus named after him in recognition of his work.

Many of the botanical specimen books in National Museum Cardiff have a fascinating history. Two contain mosses collected by Thomas Drummond on the Second Overland Arctic expedition between 1825 and 1827 to British North America (now Canada). Delving further into the book’s background reveals that the Captain, Sir John Franklin, sent Drummond to the Rocky Mountains with one Native American hunter. After the hunter left him on his own, he survived a severe winter, being mauled by a bear, and starvation. He still managed to collect, preserve and study many new plants of the North American continent. This work was published by Sir W.J. Hooker, who later became the director of the Royal Botanic Gardens, Kew.

The more recent books are systematically collected specimens known as ‘exsiccatae’. These are sets of duplicate specimens distributed by scientists to other museums. They help to spread the risk of losing a particularly important set of specimens, and to allow scientists around the world to study them. Lists of their contents are usually published in a journal or online. Much of the Berlin Herbarium and the botanical specimens within it was destroyed in World War 2, however many duplicate specimens from this collection survive in other herbaria around the world. From around the 1900s, exsiccatae changed from being bound books to being loose specimens. This meant museums receiving them could incorporate them into their collections alongside other closely related specimens for easier access and comparison.

Continuing the international year of the periodic table of chemical elements, for April we have selected Calcium. Known by most as the fundamental element in bone-forming or limestone, it has a host of other applications and is present in seabeds and marine life past and present.

Calcium (Ca) is a light-coloured metallic element with an atomic number of 20.  It is crucial for life today and commonly forms a supporting role in plants and animals. The 5^th most common element in the earth’s crust, calcium forms many useful rocks and minerals such as limestone, aragonite, gypsum, dolomite, marble and chalk.

Aragonite and Calcite, the two most commonly crystalised forms of calcium carbonate, helped form the 2 million shells in our mollusc collection, the core of which is the Melvill-Tomlin collection, donated to the museum in the 1950s. An international collection it contains many rare, beautiful and scientifically important specimens and is utilised by worldwide scientists for their research. Pearls, also made of aragonite and calcite, are produced by bivalves such as oysters, freshwater mussels and even giant clams. In nature pearls are the result of the molluscs’ reaction against a parasitic intruder or a piece of grit. The mantle around the soft bodied animal secretes calcium carbonate and conchiolin that surrounds the invading body and imitates its shape so they are not all perfectly spherical. In the pearl industry the oyster or mussel is ‘seeded’ with a tiny orbs of shell to ensure that the resulted pearl is totally spherical.

Mollusc shells are created as protective shields by their soft-bodied owners and this is true of other invertebrates, especially in the world’s oceans. Coral reefs and some marine bristle worm tubes (Serpulidae, Spirorbinae) rely on the reinforcing nature of calcium carbonate to provide support and protection to their soft bodies. Crustaceans such as crabs and lobsters have a hard exoskeleton strengthened with both calcium carbonate and calcium phosphate. Calcium required after moulting in lobsters, crawfish, crayfish and some land crabs is provided by gastroliths (sometimes referred to as gizzard stones, stomach stones or crab’s eyes). They are found on either side of the stomach and provide calcium for essential parts of the cuticle such as mouthparts and legs. The museum’s collections holds nearly 750,000 marine invertebrates, including crustaceans, corals and bristleworms.

Many of the 700,000 fossils in the Museum’s collections are also made of calcium minerals.  Invertebrates use two main forms of calcium carbonate to make their shells and exoskeletons, and the one they use influences how likely they are to be immortalised as fossils.  Aragonite, found in the shells of molluscs such as ammonites, gastropods and bivalves, is unstable and doesn’t usually survive for millions of years.  During fossilisation, aragonite shells either dissolve away completely, or the aragonite recrystallizes to form calcite.  Calcite was used to make the shells and skeletons of extinct groups of corals, articulate brachiopods, bryozoans, echinoderms and most trilobites.  It is much more stable than aragonite, so the original hard parts of these creatures are commonly found as fossils, millions of years after they sank to the sea floor.  Large calcite crystals are often found filling spaces in fossils, such as the chambers inside ammonite shells.  Vertebrates use a different calcium mineral to make their bones and teeth: apatite (calcium phosphate), which can survive for millions of years to make iconic fossils such as dinosaur skeletons and mammoth tusks.

The Museum’s rock collections contain many limestones, rocks formed at the bottom of ancient seas from bits of shells and other calcium carbonate-rich remains.  For millenia, people have used limestones as a construction material: from carved stone in the iconic Greek and Roman temples; broken fragments as ballast in the base layer of railways and roads; or burnt to form lime in the manufacturing of cement.  National Museum Cardiff and other iconic buildings in Cardiff Civic Centre were built from a famous Dorset limestone called Portland Stone.  The Museum’s floor is tiled with marble, limestone that has been transformed (‘metamorphosed’) under great heat and pressure.  Marble has long been prized by sculptors, since the ancient Greeks and Romans. The Museum’s art collections include works in this material by Auguste Rodin, John Gibson, Sir Francis Chantrey, Sir William Goscombe John, and many others. There are also important examples of work by twentieth-century sculptors, such as Jacob Epstein, Eric Gill and Henri Gaudier-Breszka. They preferred carving the softer texture and density of the softer limestone, Portland Stone and sandstone.

The Amgueddfa Cymru economic botany collection features 65 specimens of plant-based dyes and tannins. The collection includes a range of leaves, roots, petals, seeds and barks used for dyeing and tanning from around the world.

'Economic Botany' refers to a group of plants that have recognised societal benefit. The Amgueddfa Cymru-National Museum Wales economic botany collection contains over 5,500 plant-based specimens, together with 12,000 timber specimens. Categories within the collection include medicinal plants; food products; dyes and tannins; gums, resins and fibres; and seeds.

Most of the dye specimens were collected from Asia, South Africa and the West Indies as well as a few samples from South America. There is one specimen from the UK - Isatis tinctoria (Woad) from Roath Park Cardiff (1936). Most of the acquisitions of these specimens were made in 1914, 1920—22 and 1938. Only two of the specimens were added after 1938.

As well as leaves, petals, roots and fruits the collection contains a range of specimens of barks for dyeing, largely acquired in the 1920s.

Dye specimens

A number of the plant-based dye specimens originate from India including:

• The dried leaves of Indigofera tinctoria (Indigo) – one of the most famous plant dyes produces a range of blue tones.
• The roots of Rubia cordifolia (Indian madder) which produce a red dye.
• The roots of Morinda citrifolia (Al dye) which produce a yellowish colour.
• Myrobalans fruits (Terminalia chebula) which produce a yellow dye.
• The petals of Safflower (Carthamus tinctorius).

Many of these plants indicate their potential as colouring agents in their botanical names. Carthamus derives from Arabic meaning ‘dye’ whilst tinctoria is a Latin word for dyeing or staining.

The collection also includes specimens from the Caribbean including Bixa orellana (Anatto seeds) from the Dominican Republic, Gold Coast, Trinidad and Tobago; and Bursera graveolens leaves from Colombia, both of which produce a red dye.

Some of these plants are used in combination to produce enhanced tones. For example, Myrobalans (Terminalia chebula) produce a buttery yellow on their own, if added to Indigo (Indigofera tinctoria) produce a teal and with madder (Rubia cordifolia) they produce orange.

Tannins

Some barks are very high in tannin. Such barks are useful for the dyeing of cellulose fibres (such as cotton and silk). The collection features a range of barks used as tannins including:

• The powdered bark of Quercus tinctoria (North America 1921), known as Dyer’s oak.
• Haematoxylon campechianum (Log wood) (Central America and West Indies 1921) which produces a purple from the heartwood.
• Rhizophora mucronata (Mangrove) (India 1920) bark which produces a reddish brown with mordant.
• The bark of Ceriops candolleana (Tengah) (India 1920), used in Malaya within Batik dyeing for purple, brown and black colours.
• Cassia auriculata (Tanner’s Cassia) (India 1921).
• An extract of wood from Schinopsis balansae (Quebrachio) from Argentina.
• Acacia mollissima (Black Wattle) (South Africa) including bark, chopped bark, ground bark and solid mimosa extract (acquired from Kew in 1924).

The collection also includes a range of Libidibia coriaria (Divi divi) seed pods from the West Indies used for tanning and extract as dye (including specimens acquired from Kew in 1924).

Galls

The collection also contains a range of galls mainly from Southern Europe (used as tannin) mainly acquired in 1914. This includes Blue Aleppo Galls, Green Aleppo Galls, Morea galls (Greece), White Bussorah galls, Blue Smyrna galls. These oak marble galls are caused by gall wasps which puncture bark of Quercus species and lay eggs inside. As well as oak marble galls, Chinese Sumac (Rhus chinensis) are also used as tanning agents.

Galls are used in dyeing processes since they tend to be very high in tannin. Cellulose-based fabrics are often treated in a gall bath prior to adding mordant (a substance that fixes dye in fabric). This process is called ‘galling’. The fabric can then be mordanted with alum, as the tannin forms an insoluble compound with the alum and natural dye, resulting in more permanent colour.

Dyed wool specimens

The dyes and tannins collection also features a range of specimens of wool that were dyed with plants using wool from the Cambrian Mill, Felindre. This includes Weld (with tin mordant), Privet (with tin mordant), Brazil wood (with alum mordant), Onions (with tin mordant), Eucalyptus (with copper mordant), Indigo (no mordant), Madder (with tin mordant), Walnut (no mordant) alongside two red and blue cloth specimens (possibly Madder and Indigo).

Tin can produce very bright natural colours. However, in excess it can make wool brittle and it is also harmful, potentially causing irritation to skin, eyes and respiratory system and damage to the liver and kidney system. Of note are the two specimens (Walnut and Indigo) that are ‘substantive’ rather than ‘fugitive’. Substantive dyes do not require a mordant.  

In 2017-2018 Poppy Nicol worked with Heather Pardoe to explore the economic botany collection and its relevance for helping us understand biodiversity and the importance of plants for health and well-being. You can read more about the Sharing Stories Sharing Collections Project here.

Have a look back at previous posts about this collection:

• The Launch of the People and Plants Exhibition
• An Introduction to the Economic Botany Collection

This article is by Dr. Poppy Nicol, a visiting researcher from Cardiff University.

This week marks the launch of the exhibition ‘People and Plants’ in the Insight Gallery, National Museum Cardiff and accompanying public report ‘Sharing Stories, Sharing Collections.’

The exhibition and report are outcomes of a collaborative placement between the Sustainable Places Research Institute and Amgueddfa Cymru-National Museum Wales funded by the National Environment Research Council Valuing Nature Programme.

During the placement, Dr. Poppy Nicol (Sustainable Places Research Institute) spent four months within the Natural Science Department at National Museum Cardiff. Poppy worked with Principal Curator Dr. Heather Pardoe and other members of the Botany team to investigate the Amgueddfa Cymru economic botany collection and its potential role it can play in supporting, valuing and understanding of biodiversity. As part of the placement, Poppy and Heather conducted a series of workshops with community groups and interviews, with the aim of exploring how future activities associated with the economic botany collection can further societal understanding and valuing of biodiversity and address the Museum’s duty of well-being.  

Drawing upon the findings of the placement, the exhibition offers insight into the Amgueddfa Cymru economic botany collection and the important role of plants in society.  

Health, well-being and plants

The Amgueddfa Cymru economic botany collection includes over 5,500 specimens of medicinal plants, food products, fibres, seeds, gums, dyes and resins, most of which were acquired between the nineteenth century and present day. The selected specimens in the ‘People and Plants’ exhibition highlights the role of plants in supporting the health and well-being of past, present and future generations.

Plant-based Remedies: old and new

The economic botany collection contains over 700 medicinal plant specimens including a Materia Medica (donated by Professor Terence Turner, Cardiff School of Pharmacy and Pharmaceutical Sciences). The exhibition features a range of plant specimens used medicinally – including quinine (used for treating malaria), star anise (containing a compound used for treating influenza) and senna pods (a traditional laxative).

It also features a contemporary example of a plant-based compound for medicinal purposes – the daffodil (Narcissus pseudonarcissus). Although toxic if consumed raw, it contains galantamine which is used in the treatment of the early stage of Alzheimer’s disease.

Biocultural diversity: heritage grains

The exhibition also showcases some of the specimens within the Museum’s economic botany seed collection - which contains over 2,700 seed specimens. The collection includes a range of wheat, barley, oat and rye varieties acquired from the Welsh Plant Breeding Station. Hen Gymro, an old wheat variety affectionately known as “Old Man’s Beard” was cultivated in South Wales into the 1920’s, said to have thrived in South Wales. With predicted changing climates and the urgent need for more ecological growing approaches, perhaps some of these old grain varieties might be of value for future farmers and growers. The exhibition highlights the importance of safeguarding biodiversity – of both wild and cultivated crops and wild species.

Sharing Stories, Sharing Collections

The accompanying report to the exhibition, ‘Sharing Stories, Sharing Collections’ by Poppy, highlights how bio-cultural collections have the potential to support public understanding and valuing of biodiversity. It suggests recent legislation in the form of the Well Being of Future Generations Act (Wales) (2015) presents opportunity for Amgueddfa Cymru-National Museum Wales to become a global innovator in terms of curating bio-cultural collections.

The report identifies clear interest in the Amgueddfa Cymru economic botany collection amongst the public. It identifies a number of opportunities for innovation in bio-cultural and economic botany collections including research-driven curation; inter-generational learning programmes; and, innovative and participatory approaches to digitisation. Inter-disciplinary collaboration with other centres of learning particularly present great opportunities to share and enhance the value of the collection. Such innovations will improve the role of the collection in supporting public valuing and understanding of biodiversity and the health and well-being of future generations.

In an era where biodiversity is being eroded, bio-cultural collections have a crucial societal role of developing understanding and valuing of biodiversity through raising public awareness of the crucial role of plants in supporting livelihoods, supporting health and well-being, maintaining ecosystem services and adapting to global environmental change.

You can see the People & Plants exhibition at National Museum Cardiff until Sunday 17 March.

Read more about the start of the project in this February 2018 blog post.